Should i tell his wife?

[Juniper]

Don't tell his wife. She probably won't believe you anyway.

But you should absolutely tell HIM.

Just e-mail him or text: "So, I found out that everything you told me was a lie. It's a real shame that you think it's okay to do that, especially when you're doing the same to your poor wife who just had a baby last year. You're a jackass. Don't EVER contact me again or I WILL tell your wife everything. I know who she is and I know how to contact her in a way you can't intercept. So disappear."

Then block him off EVERYTHING.

I say this because he WILL try to convince you that his wife is just crazy, that they really are separated and she just can't let go, and that the baby isn't even his. Either that or he'll just get mad and call you a psycho stalker. Either way, don't give him a way to respond. Say your piece - do NOT let on that you're hurt otherwise he gets an ego boost he doesn't deserve - and let that be it.